Relay switch



1961 I J. R. MCKINNEY 2,973,417

RELAYSWITCH Filed Nov. 25, 1958 Q mvzm'onz JOHN R. M KINNEY ATTYS.

United States Patent RELAY SWITCH John R. McKinney, 111 Brittany Drive, Chalfont, Pa.

Filed Nov. 25, 1958, Ser. No. 776,244 7 Claims. (Cl. 200-112) The present invention relates generally to mercury type relay switches, and more particularly to improvements in the plunger or armature assembly used in switches of this type.

Briefly the present invention pertains to mercury contact relays having a plunger or armature adapted to be actuated axially within a casing, between circuit making and circuit breaking positions, in response to an electromagnetic solenoid. More particularly the class of relay herein illustrated comprises a glass envelope having a body of mercury within its lower end, a pair of electrodes one of which is normally immersed, the other which is floatingly supported by the mercury. An electromagnetic solenoid surrounds the base of the glass envelope, and when energized causes the plunger to sink into the body of mercury and displace the same upwardly thereby establishing a mercury to mercury contact between the electrodes. In order to insure reliable response of the plunger it is essential that the frictional resistance to its movement within the envelope be a minimum.

Various means have been employed to minimize the frictional engagement such, for example, as metal protrusions formed on the plunger for establishing point contact between the plunger and the interior of the envelope. These arrangements have not been entirely satisfactory for the reason that the metal protrusions have a tend- "ice plunger rises, thereby minimizing the possibility of reestablishing contact between the electrodes when the solenoid is deenergized. Accordingly the present invention provides a means for maintaining better alignment of the plunger in the tubular envelope, precludes faulty operation of the plunger, as discussed above, and minimizes vibration and noise.

With the foregoing in mind, an object of the present invention is to provide a new and improved means for reducing deleterious frictional engagement between the plunger of a mercury type relay and the glass envelope in which the plunger operates.

Another object of the present invention is to provide an improved type plunger assembly wherein reliable and immediate movement of the plunger is assured upon actuation, the assembly providing a damping action during movement of the plunger.

A further object of the present invention is to provide a plastic guide member that may be readily used with plungers of a conventional mercury typerelay.

These and other objects of the present invention and the various features and details of the construction and operation are more fully set forth hereinafter with reference to the accompanying drawings, in which:

Fig. 1 is an elevational view partially in section, showing an embodiment of the present invention;

Fig. 2 is a perspective view showing the plunger in phantom and the helicoil positioned thereon; and

Fig. 3 is a sectional view taken along line 3-3 of Fig. 2.

Referring more specifically to the drawings and particulariy to Fig. 1 thereof, reference numeral 10 desig hates generally a relay switch which is suitably mounted within an electromagnetic solenoid 11. The envelope 12 supports a body of mercury 12a in its lower end. The switch 10 includes a sealed tubular housing or envelope 12, preferably made of glass and a pair of lead-in wires 13 and 14 preferably of tungsten or molybdenum. The

enc over a period of use, to abrade the glass in the 1 form of an interior ring due to minor agitation of the plunger. The plunger has a tendency on occasion to stick in the depressed position, possibly due to this interior ring, so that contact is not immediately broken. Further when the solenoid is deenergized, the plunger rises rapidly in the mercury and ofttimes there is a resultant oscillation of the plunger prior to coming to rest and which may reestablish contact between the electrodes. Additionally noise and vibrations develop because of the metal to glass contact.

In accordance with the present invention a new, different and improved means for insuring reliable movement of the plunger within the glass envelope is provided. This means comprises a member including at least an outer covering made of a resilient plasticmaterial such as, for example, polytritluorochloroethylene (sold under the trade name Kel-F by the M. W. Kellogg Co.), or polytetrafluoroethylene (sold under the trade name Teflon, by the E. I. du Pont de Nemours & Co.). This plastic member is so arranged that it extends radially beyond the exterior surface of the plunger to thereby provide a sort of lubricant and spacer between the plunger and the interior of the tubular envelope. Although not limited to the helicoil (spiral configuration) shown, the helical arrangement is preferable for the reason that it causes a turning movement of the plunger upon actuation in either direction, thereby minimizing wear of the contact and/or contact between the plastic member and any one spot on the tube. Additionally the threaded or helical configuration provides a damping action as the lead-in wires 13 and 14 are connected to electrode contacts 15 and 16 respectively which are pinch sealed in the lower part of the envelope 12 and extended upwardly therein. One of the electrodes 15 extends upwardly into the envelope only a short distance so that it is normally, in operation, completely immersed in the mercury 12a, and the other electrode 16 extends upwardly inside a sealed insulating sleeve 17 of glass or the like so that it normally protrudes above the level of the mercury 12a. A cup 17a is formed in the upper end of sleeve 17, surrounding the upper end of electrode 16 and adapted to contain a small amount of mercury. The electrodes are adapted to be bridged and unbridged, in a mercury to mercury contact, by action of the mercury 12a in a manner to be described later.

A plunger or armature assembly 18 is floatingly supported for axial movement within the glass envelope by the body of mercury. The plunger is generally cylindrical so that it may engage over the electrode 16 and be moved longitudinally thereof. The plunger comprises an exterior metal shell or cage 19 of substantially cylindrical configuration which is crimped over at its lower end to contain a liner 20 made of a ceramic or some other non-magnetic material. The exterior shell is split along its length to allow for differences in thermal expansion between the metal shell and ceramic liner. The shell or cage 19 can be formed with upper and lower encircling rows 21 of radially projecting protru sions 22, each comprising a substantially semispherical outer surface. The protrusions 22 are formed in the side wall of the shell adjacent the upper and lower ends thereof. The provision of the protrusions is not essential to the invention however, and may be eliminated.

In order to illustrate operation of the relay switch described, assume that the switch parts are in stable equilibrium with the electromagnetic solenoid deenergized. In this position the plunger 18 is floatingly supported by the mercury, and electrode 16 extends above the level of the mercury, and electrode 15 is completely immersed therein. In this position the circuit is open since there exists no contact between the electrodes, electrode 16 being insulated from the mercury by the sleeve 17. Assume now that the solenoid is energized. Energization of the solenoid creates a magnetic field which attracts the plunger 18, by acting on metal cage 1?, and urges it downwardly toward the base of the envelope. The level of mercury in turn will rise, due to downward displacement of the plunger 18, and cause electrode 16 to be submerged, thereby establishing a mercury to mercury contact between the electrodes and closing the circuit.

1 Assume now that the coil is deenergized. Immediately the plunger will rise, due to its buoyancy, and the mercury level in envelope 12 drops to a position below the level of electrode 16. The circuit will now be open since the contact between the electrodes is broken.

In accordance with the present invention, means are .provided to insure quick, reliable and substantially friction-free movement of the plunger within the glass envelope upon energization and deenergization of the solenoid. To this end the plunger 18 is surrounded by means in the nature of a guide member 25 which forms 'a' sort of lubricant and spacer between the plunger and the interior of the tubular envelope. In the embodiment shown in the drawing, the guide member 25 comprises a ,helicoil 26 (wire helix) or spring-wound about the plunger intermediate the upper and lower rows of protrusions. The .wire is-provided in sections, with a plastic outer covering 27 which can, for example, be in the nature of known spaghetti form and greater than 360 of coverage around the upper and lower portion of the plunger is provided. The cross-section of the helical guide member is of sutlicient thickness so that the outer periphery extends beyond the protrusions 22 formed on the shell 19. The helical guide member is positioned on the cage intermediate the rows of protrusions, it formed in the wall of "the shell 19, adjacent the upper and lower ends thereof. The covered helical spring or wire is maintained in place due to spring tension and the exposed portion of the spring grips the metal of cage 19. Where protrusions are used they will additionally'serve to locate the guide member. As noted previously the plastic material which is substantially inert acts as a lubricant, maintains a more precise alignment of the plunger in the tube and minimizes vibration and noise. Additionally abrasion of the glass tube due to plunger activity is eliminated and consequently malfunctions due to sticking of the plunger resulting from abraded areas is avoided. Under some circumstances coverage of the plastic material around the shell 19. can be less than 360, especially at the bottom, to allow the mercury to run off when the plunger IS in up position in a tight fitting tube.

Although other configurations of the plastic material could be used, as for example external rings, plugs, etc., the spiral arrangement is preferable for reason that this configuration provides a damping action as the plunger rises, thereby eliminating the possibility of reestablishing contact because of plunger oscillation as discussed previously.

While a particular embodiment of the present invention has been illustrated and described herein, it is not intended to limit the invention to such a disclosure and 4 changes and modifications may be incorporated and embodied therein within the scope of the following claims.

I claim:

1. In a plunger assembly for a mercury relay or the like adapted to be mounted within an enclosed tubular envelope having mercury therein, a cylindrical plunger sleeve of magnetic material, and means in the form of a guide member operatively associated with the outer periphery of said sleeve, said means comprising a fluoroethylene polymer and preventing engagement of said sleeve and the interior of said tubular envelope.

2. In a plunger assembly for a mercury relay or the like adapted to be mounted within an enclosed tubular envelope having mercury therein, a cylindrical plunger sleeve of magnetic material, and a guide member helically wound about the outer periphery of said sleeve and preventing engagement of said sleeve and the interior of said tubular envelope.

'3. In a plunger assembly for a mercury relay or the like adapted to be mounted within an enclosed tubular envelope having mercury therein, a cylindrical sleeve, a pair of encircling rows of protrusions projecting radially outwardly of the outer periphery of said sleeve, one row in proximity to each end of said sleeve, and means in the form of a guide member spaced intermediate the rows of protrusions and helically wound about the outer periphery of said sleeve and extending radially outward beyond saidprotrusions and preventing engagement of said sleeve and tubular envelope.

4. In a plunger assembly for a mercury relay or the like adapted to be mounted within an enclosed tubular envelope having mercury therein, a cylindrical sleeve of magnetic material, and a helicoil covered with a plastic material encircling said sleeve and preventing engagement of said cylindrical sleeve and the tubular envelope.

5. The combination in an electrical switch of an enclosed generally tubular glass envelope, a pool of mercury in said envelope, spaced electrode contacts mounted within said envelope adapted to form a closed circuit through the mercury, a plunger mounted in said envelope for movement axially thereof, means for actuating said plunger to vary the level of mercury in said envelope and thereby etfect a mercury to mercury connection between the contacts and thereby close the circuit, said plunger comprising a generally cylindrical sleeve of magnetic material and means in the form of a guide member covered with a fluoroethylene polymer helically wound about the outer periphery of said sleeve and preventing engagement of said sleeve and tubular envelope.

6. In a plunger assembly for a mercury relay or the like adapted to be mounted within an enclosed tubular envelope having mercury therein, a cylindrical sleeve of magnetic material, and a helicoil covered at its end portions with a plastic material encircling said sleeve and preventing engagement of the cylindrical sleeve and the tubular envelope, said plastic cover encircling said cylindrical sleeve more than 360 about its periphery.

7. In a plunger assembly for a mercury relay or the like adapted to be mounted within an enclosed tubular envelope having mercury therein, a cylindrical plunger sleeve of magnetic material, and a fluoroethylene polymer guide member helically wound about the outer periphery of said sleeve and preventing engagement of said sleeve and the interior of said tubular envelope.

References Cited in the file of this patent UNITED STATES PATENTS 2,060,811 Larson Nov. 17, 1936 

